(a) Field of the Invention
The present invention relates to a device and method for optical supervisory channel framing in an optical transport network system. More specifically, the present invention relates to a device and method for optical supervisory channel framing in a multi-channel wavelength division multiplexing system.
(b) Description of the Related Art
Recently, the ITU-T (International Telecommunication Union-Telecommunication Standardization Sector) has been developing standardization in regard to the supervisory channel operation for optical signal maintenance by sections in the optical transport network environment.
The optical supervisory channel in the optical transport network system transports optical transport module overhead signals, which are overhead signals of an optical transmission section, an optical multiplex section, and an optical channel optical channel section.
The optical supervisory channel also transports a signaling communication channel for the control plane of the optical transport network, a message communication channel, a protection communication channel, and an automatic laser power control channel.
FIG. 1 is a schematic of a general optical transport network system, in which the configuration of a wavelength division multiplexing system is illustrated.
The conventional optical transport network system comprises, as shown in FIG. 1, a terminal WDM (Wavelength Division Multiplexing) system 10 and a repeater 20, which are connected to each other through an optical line 30.
More specifically, the terminal WDM system 10 comprises an optical channel section 11, an optical multiplex section 12, an optical transmission section 13, a first WDM coupler 14, and an optical supervisory channel section 15. The repeater 20 comprises a second WDM coupler 21, an optical transmission section 22, a third WDM coupler 23, and an optical supervisory channel section 24.
The operation of the optical transport network system as constructed above is described as follows. First, the optical transmission section 13 amplifies a multiplexed optical signal from the optical multiplex section 12 to a predetermined level, and the first WDM coupler 14 couples the amplified optical signal received from the optical transmission section 13 to an optical supervisory channel signal from the optical supervisory channel section 15, and transmits the coupled signals to the repeater 20.
In the repeater 20, the second WDM coupler 23 divides the received optical signals into a main optical signal and an optical supervisory control signal. The optical transmission section 22 amplifies the main optical signal to a predetermined level, and the optical supervisory channel section 24 receives the optical supervisory channel signal.
Subsequently, the third WDM coupler 23 couples the amplified optical signal to the optical supervisory channel signal and transmits the coupled signals to another repeater or another WDM system in the optical transport network system.
However, the conventional optical transport network system of the above configuration and operation separately operates optical supervisory channels transporting the section-specific overhead signals, which can cause some problems in regard to the dissipation of resources and the deterioration of efficiency in transporting a single optical transport module overhead signal to the respective sections.
In addition, the conventional optical transport network system simply suggests a method of inserting or extracting optical supervisory channels to or from an optical line, but never takes into consideration how to effectively transport maintenance signals received from the respective sections (e.g., the optical channel section, the optical multiplex section, and the optical transmission section) by the optical supervisory channel device in the optical transport network system, or how to extract maintenance signals from the received optical supervisory channel frame and to transport them to the respective sections.
Namely, the conventional optical transport network system receives overhead signals for maintenance of the section-specific optical signals from the central CPU and transports them to each section-specific CPU. Hence, the maintenance signals for the main optical signal are transferred to each section-specific CPU after a predetermined time has elapsed, resulting in the waste of a great deal of time and resources in controlling the optical transport network plane using the maintenance signals.
In addition, the conventional optical transport network system cannot multiplex the overhead signals received from the respective sections and the optical supervisory channel overhead signal from the optical supervisory channel device in the system into a single multiplexed signal. Hence, the conventional optical transport network system must transfer the respective overhead signals through the section-specific optical supervisory channels so as to transfer the optical transport module overhead signals to another repeater or another terminal WDM system.